计算方位角 返回角度

//计算方位角  返回角度
        private double ComputeAzimuthAngle(double FromPntX, double FromPntY, double ToPntX, double ToPntY)
        {
            double jiao;
            double ab = 0.0;
            double dx;
            double dy;
            dx = ToPntX - FromPntX;//计算增量
            dy = ToPntY - FromPntY;
            jiao = Math.Abs(dx / dy);
            if (dx > 0 && dy > 0)//四个象限的不同情况  第一象限
            {
                ab = Math.Atan(jiao);
            }
            if (dx == 0 && dy > 0)
            {
                ab = 0;
            }
            if (dx < 0 && dy > 0)  //第四象限
            {
                ab = 2 * Math.PI - Math.Atan(jiao);
            }
            if (dx > 0 && dy == 0)
            {
                ab = Math.PI / 2;
            }
            if (dx == 0 && dy == 0)
            {
                ab = 0;
            }
            if (dx < 0 && dy == 0)
            {
                ab = Math.PI + Math.PI / 2;
            }
            if (dx < 0 && dy < 0)  //第三象限
            {
                ab = Math.Atan(jiao) + Math.PI;
            }
            if (dx == 0 && dy < 0)
            {
                ab = Math.PI;
            }
            if (dx > 0 && dy < 0)  //第二象限
            {
                ab = Math.PI - Math.Atan(jiao);
            }
            ab = ab / Math.PI * 180;//弧度转角度
            return ab;
        }